The present invention concerns testing of electronic devices and pertains particularly to automated testing of a frequency converter device.
A frequency converter device is used to convert a signal in one frequency range to a signal in another frequency range. For example, a typical frequency converter device uses a mixer to down-convert or up-convert an input signal to an output signal.
For a down-conversion of a high radio frequency (RF) signal to an intermediate frequency (IF) the mixer combines the RF signal with a local oscillator (LO) signal to produce a sum and a difference. The difference gives the down-converted signal.
For an up-conversion of an IF to an RF signal, the mixer combines the IF signal with the LO signal to produce a sum and a difference. The sum gives the up-converted signal.
Various types of testers can be used to test frequency converter devices. For example, a network analyzer can be used to provide input to and measure the output from a frequency converter device. Alternatively, any testing device with the capability to provide input to and measure the output from a frequency converter device can be used.
When stimulated at an input and LO (local oscillator) port, a frequency converting device produces a number of mixing products that show up at the output. These include not only the fundamental mixing products, but harmonics and spurs as well as leakage from the input and LO signals. The user of a tester is typically interested in both the desired output, termed the “fundamental” and one or more of the other mixing products.
When testing a frequency converter device, a user is generally required to specify to the testing device a frequency range of interest for the output signal of the frequency converter device. This can generally be derived from the input signal and the LO signal. However, performing the computations and then appropriately setting the testing device can be inconvenient and cumbersome. Additional complexity is added when determining the expected output from a frequency converter that includes more than one mixer.